In order to obtain a better understanding of the subject invention the following data is submitted for the purpose of comparing its attributes, for example, with various types of cutter heads, manufactured and sold by the Urschel Laboratories Inc. of Valparaiso, Ind. which are exemplified in certain earlier Patents:
Cutting heads have heretofore been made by what may be referred to as a method A are described in U.S. Pat. No. 2,938,558 issued May 31, 1960. The cutting heads in this Patent were machined from a solid piece of steel. Various types of configurations are described in the Patent and all of them produced too much friction on the product being cut which resulted in excessive heat produced in the product. When cutting meat with such cutting heads, the fat portion of the meat was smeared over the lean portion resulting in a product with poor appearance. Excessive amounts of time was also required to machine these cutting heads which resulted in a high cost and a resulting high selling price.
Cutting heads made by what may be termed a method B are described in U.S. Pat. No. 2,875,800 issued Mar. 3, 1959. The heads in this Patent were made up of flat circular rings and flat rectangular knives. The various parts were held together with bolts. From a practical consideration, it would have been extremely difficult to make these to cut a product into small flakes. The reason for this is that too many parts would have been required and these parts would be so thin in cross section that the parts would be easily bent and broken in use. The cost of making the many parts would be too high resulting in a high price for the assembled cutting heads.
Cutting heads made by a method termed C are described in U.S. Pat. Nos. 3,196,916 issued July 27, 1965 and No. 3,255,646 issued June 14, 1966. The cutting heads shown in these Patents are made up of segments which are stamped out on a punch press, they are then stacked and held together with rivets while being welded together in a furnace. These cutting heads have been successfully manufactured over a period of years and are highly suitable for a large number of applications. There are, however, several disadvantages to making cutting heads by this method. Since there are as many as 4,000 segments in certain cutting heads, the cost of stacking the segments is high. Some desirable metal alloys with suitable hardness and wear resistance cannot be stamped on a punch press without breaking the segments into pieces. There is no practical way to place a taper on the surfaces of the segments. Because of this, the cut product must be ejected from the cutting head through passages having parallel surfaces. Rather than having the cut pieces of product ejected in free flight the product jams between the parallel surfaces and the product is extruded in a compressed form from the cutting head. This is turn causes excessive power to be used resulting in appreciable heating of the product being cut, smearing the surface of the cut product and crushing the tissue of the cut product.
Cutting heads made by an improved method are described in the subject application. By utilizing this improved method, the three disadvantages inherent in the cutter heads alluded to above are overcome. The present method used is to cast the cutting head in one piece by use of investment casting. The cutting heads are cast from hard, stainless materials. Although other methods may be used for making these precision castings, investment casting seems to be the only practical method at this time. After the castings are made, very little work is required to finish them. It is only necessary to grind the top and bottom of the cutting heads to make them flat and parallel and then to grind an internal cylindrical surface to sharpen the internal knives or cutting edges. Investment casting is a casting method designed to achieve high dimensional accuracy by making a mold of refractory slurry, which sets at room temperature, surrounding a wax pattern which is then melted out to leave a mold without joints. In making the cutting heads, the mold is heated to about 1,800.degree. F and metal is poured into it at about 2,800.degree. F. The wax patterns are made by injecting hot wax under pressure into a cavity fixture. The fixture is composed of several pieces of metal. There is a top and bottom plate, a central core and a number of pieces to form the outside configuration of the wax pattern cutting head.